WO2013006006A2 - Method and apparatus for transmitting a signal in a wireless communication system - Google Patents

Abstract

One embodiment of the present invention relates to a method for transmitting a signal to an unlicensed band of a base station in a wireless communication system. The method comprises the steps of: transmitting at least one of a preamble and a reservation signal, if it is determined through carrier sensing that the unlicensed band is available; and transmitting a PDSCH on the unlicensed band immediately after the transmission of at least one of the preamble and the reservation signal. The preamble enables a terminal to acquire reception synchronization for at least one of the reservation signal and the PDSCH.

Description

Method and apparatus for signal transmission in wireless communication system

The following description relates to a signal transmission method and apparatus for the same in a wireless communication system.

Wireless communication systems are widely deployed to provide various kinds of communication services such as voice and data. In general, a wireless communication system is a multiple access system capable of supporting communication with multiple users by sharing available system resources (bandwidth, transmission power, etc.). Examples of multiple access systems include code division multiple access (CDMA) systems, frequency division multiple access (FDMA) systems, time division multiple access (TDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, and single carrier frequency (SC-FDMA). division multiple access (MCD) systems and multi-carrier frequency division multiple access (MC-FDMA) systems.

The present invention relates to a signal transmission method on an unlicensed band and an apparatus therefor.

The technical problems to be achieved in the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned above will be clearly understood by those skilled in the art from the following description. Could be.

According to a first technical aspect of the present invention, in a method for transmitting a signal on an unlicensed band by a base station in a wireless communication system, when it is determined that the unlicensed band is available through carrier sensing, at least one of a preamble or a reserved signal Transmitting one or more; Transmitting a PDSCH on an unlicensed band immediately after transmission of at least one of the preamble or a reservation signal, wherein the preamble is for a terminal to obtain reception synchronization of at least one of the reservation signal or the PDSCH. The transmission method.

According to a second aspect of the present invention, there is provided a method for a terminal to receive a signal on an unlicensed band in a wireless communication system, the method comprising: receiving at least one of a preamble or a reservation signal from a base station on the unlicensed band; And receiving a PDSCH on the unlicensed band, wherein the terminal acquires reception synchronization of at least one of the reservation signal or the PDSCH through the preamble.

A third technical aspect of the present invention is a base station apparatus in a wireless communication system, comprising: a transmission module; And a processor, wherein the processor transmits at least one or more of a preamble or a reservation signal when the unlicensed band is determined to be available through carrier sensing, and immediately after the transmission of at least one of the preamble or the reservation signal. Transmit the PDSCH on the band, wherein the preamble is a base station device for the terminal device to obtain the reception synchronization of at least one of the reservation signal or the PDSCH.

A fourth technical aspect of the present invention is a terminal device in a wireless communication system, comprising: a receiving module; And a processor, wherein the processor is configured to receive at least one or more of a preamble or a reservation signal from a base station on the unlicensed band and receive a PDSCH on the unlicensed band, wherein the reservation signal or the PDSCH is received. A terminal device for acquiring at least one reception synchronization.

The first to fourth technical aspects of the present invention may include all of the following.

When the preamble is transmitted prior to the reservation signal, the preamble may include information indicating that transmission of the reservation signal is started.

When the preamble is transmitted after the reservation signal, the preamble may be transmitted at the subframe boundary of the licensed band used by the base station.

If the time point at which the unlicensed band is determined to be available is one of a subframe boundary or a slot boundary of the licensed band used by the base station, the reservation signal may not be transmitted.

Scheduling information of the PDSCH transmitted on the unlicensed band may be transmitted through a PDCCH transmitted on a licensed band used by the base station.

The preamble may further include identifier information of a terminal that receives the PDSCH.

According to the present invention, even when the time point at which the signal is to be transmitted on the unlicensed band and the time point at which the unlicensed band is available are inconsistent, the signal can be efficiently transmitted on the unlicensed band. In addition, it is possible to accurately obtain the synchronization of the reservation signal and data transmission transmitted to secure resources on the unlicensed band.

The effects obtainable in the present invention are not limited to the above-mentioned effects, and other effects not mentioned above may be clearly understood by those skilled in the art from the following description. will be.

1 is a diagram for explaining the structure of a radio frame.

FIG. 2 is a diagram illustrating a resource grid in a downlink slot.

3 is a diagram illustrating a structure of a downlink subframe.

4 is a diagram illustrating a structure of an uplink subframe.

5 is a diagram illustrating a format in which PUCCH formats are mapped in an uplink physical resource block.

6 is a diagram illustrating an example of determining a PUCCH resource for ACK / NACK.

7 is a diagram illustrating a structure of an ACK / NACK channel in the case of a normal CP.

8 is a diagram illustrating a structure of a CQI channel in the case of a normal CP.

9 illustrates a PUCCH channel structure using block spreading.

10 is a diagram for explaining a downlink reference signal.

11 is a diagram for explaining a sounding reference signal.

12 is a diagram for describing resource partitioning for a relay.

13 is a diagram for describing carrier aggregation.

14 is a diagram for describing cross carrier scheduling.

15 is a diagram for describing a method of transmitting uplink control information through a PUSCH.

FIG. 16 is a diagram illustrating a multiplexing process of data and control information for uplink transmission.

17 is a schematic diagram of an entire system according to an embodiment of the present invention.

18 is a diagram for explaining PDSCH transmission in an unlicensed band according to Embodiment 1 of the present invention.

19 to 21 are diagrams for explaining PDSCH transmission in an unlicensed band according to Embodiment 2 of the present invention.

FIG. 22 illustrates PUSCH transmission in an unlicensed band according to Embodiment 3 of the present invention. FIG.

FIG. 23 illustrates a case where OFDMA is applied to embodiments of the present invention.

24 to 26 are diagrams for explaining preamble transmission in PDSCH transmission in an unlicensed band according to an embodiment of the present invention.

27 is a view for explaining a carrier sensing unit that can be applied to embodiments of the present invention.

FIG. 28 illustrates sharing of a carrier sensing result applicable to embodiments of the present invention.

29 is a diagram showing the configuration of a base station apparatus and a terminal apparatus according to an embodiment of the present invention.

The following embodiments combine the components and features of the present invention in a predetermined form. Each component or feature may be considered to be optional unless otherwise stated. Each component or feature may be embodied in a form that is not combined with other components or features. In addition, some components and / or features may be combined to form an embodiment of the present invention. The order of the operations described in the embodiments of the present invention may be changed. Some components or features of one embodiment may be included in another embodiment or may be replaced with corresponding components or features of another embodiment.

In the present specification, embodiments of the present invention will be described based on a relationship between data transmission and reception between a base station and a terminal. Here, the base station has a meaning as a terminal node of the network that directly communicates with the terminal. The specific operation described as performed by the base station in this document may be performed by an upper node of the base station in some cases.

That is, it is obvious that various operations performed for communication with a terminal in a network composed of a plurality of network nodes including a base station may be performed by the base station or other network nodes other than the base station. A 'base station (BS)' may be replaced by terms such as a fixed station, a Node B, an eNode B (eNB), an access point (AP), and the like. Relay can be replaced by terms such as Relay Node (RN), Relay Station (RS). In addition, the term “terminal” may be replaced with terms such as a user equipment (UE), a mobile station (MS), a mobile subscriber station (MSS), a subscriber station (SS), and the like.

Specific terms used in the following description are provided to help the understanding of the present invention, and the use of such specific terms may be changed to other forms without departing from the technical spirit of the present invention.

In some instances, well-known structures and devices may be omitted or shown in block diagram form centering on the core functions of the structures and devices in order to avoid obscuring the concepts of the present invention. In addition, the same components will be described with the same reference numerals throughout the present specification.

Embodiments of the present invention may be supported by standard documents disclosed in at least one of the wireless access systems IEEE 802 system, 3GPP system, 3GPP LTE and LTE-Advanced (LTE-A) system and 3GPP2 system. That is, steps or parts which are not described to clearly reveal the technical spirit of the present invention among the embodiments of the present invention may be supported by the above documents. In addition, all terms disclosed in the present document can be described by the above standard document.

The following techniques include code division multiple access (CDMA), frequency division multiple access (FDMA), time division multiple access (TDMA), orthogonal frequency division multiple access (OFDMA), single carrier frequency division multiple access (SC-FDMA), and the like. It can be used in various radio access systems. CDMA may be implemented with a radio technology such as Universal Terrestrial Radio Access (UTRA) or CDMA2000. TDMA may be implemented with wireless technologies such as Global System for Mobile communications (GSM) / General Packet Radio Service (GPRS) / Enhanced Data Rates for GSM Evolution (EDGE). OFDMA may be implemented in a wireless technology such as IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802-20, Evolved UTRA (E-UTRA). UTRA is part of the Universal Mobile Telecommunications System (UMTS). 3rd Generation Partnership Project (3GPP) long term evolution (LTE) is part of an Evolved UMTS (E-UMTS) using E-UTRA, and employs OFDMA in downlink and SC-FDMA in uplink. LTE-A (Advanced) is the evolution of 3GPP LTE. WiMAX can be described by the IEEE 802.16e standard (WirelessMAN-OFDMA Reference System) and the advanced IEEE 802.16m standard (WirelessMAN-OFDMA Advanced system). For clarity, the following description focuses on 3GPP LTE and 3GPP LTE-A systems, but the technical spirit of the present invention is not limited thereto.

1 is a diagram illustrating a structure of a radio frame used in a 3GPP LTE system. Referring to FIG. 1A, one radio frame includes 10 subframes, and one subframe includes two slots in the time domain. The time for transmitting one subframe is defined as a transmission time interval (TTI). For example, one subframe may have a length of 1 ms, and one slot may have a length of 0.5 ms. One slot may include a plurality of OFDM symbols in the time domain. Since the 3GPP LTE system uses the OFDMA scheme in downlink, the OFDM symbol represents one symbol length. One symbol may be referred to as an SC-FDMA symbol or a symbol length in uplink. A resource block (RB) is a resource allocation unit and includes a plurality of consecutive subcarriers in one slot. The structure of such a radio frame is merely exemplary. Accordingly, the number of subframes included in one radio frame, the number of slots included in one subframe, or the number of OFDM symbols included in one slot may be changed in various ways.

Figure 1 (b) illustrates the structure of a type 2 radio frame. Type 2 radio frames consist of two half frames. Each half frame consists of five subframes, a Downlink Pilot Time Slot (DwPTS), a Guard Period (GP), and an Uplink Pilot Time Slot (UpPTS), of which one subframe consists of two slots. . DwPTS is used for initial cell search, synchronization or channel estimation at the terminal. UpPTS is used for channel estimation at the base station and synchronization of uplink transmission of the terminal. The guard period is a period for removing interference generated in the uplink due to the multipath delay of the downlink signal between the uplink and the downlink.

The structure of the radio frame is merely an example, and the number of subframes included in the radio frame or the number of slots included in the subframe and the number of symbols included in the slot may be variously changed.

FIG. 2 is a diagram illustrating a resource grid in a downlink slot. One downlink slot includes seven OFDM symbols in the time domain and one resource block (RB) is shown to include 12 subcarriers in the frequency domain, but the present invention is not limited thereto. For example, one slot includes 7 OFDM symbols in the case of a general cyclic prefix (CP), but one slot may include 6 OFDM symbols in the case of an extended-CP (CP). Each element on the resource grid is called a resource element. One resource block includes 12 × 7 resource elements. The number of NDLs of resource blocks included in a downlink slot depends on a downlink transmission bandwidth. The structure of the uplink slot may be the same as the structure of the downlink slot.

3 is a diagram illustrating a structure of a downlink subframe. Up to three OFDM symbols at the front of the first slot in one subframe correspond to a control region to which a control channel is allocated. The remaining OFDM symbols correspond to data regions to which a physical downlink shared channel (PDSCH) is allocated. Downlink control channels used in the LTE system include, for example, a physical control format indicator channel (PCFICH), a physical downlink control channel (PDCCH), a physical HARQ indicator channel (PCH). Physical Hybrid automatic repeat request Indicator Channel (PHICH).

The PCFICH is transmitted in the first OFDM symbol of a subframe and includes information on the number of OFDM symbols used for control channel transmission in the subframe.

The PHICH includes a HARQ ACK / NACK signal as a response of uplink transmission. The PDCCH transmits downlink control information (DCI). The DCI may include uplink or downlink scheduling information or include an uplink transmission power control command for an arbitrary terminal group according to a format.

DCI format

Currently, according to LTE-A (release 10), DCI formats 0, 1, 1A, 1B, 1C, 1D, 2, 2A, 2B, 2C, 3, 3A, and 4 are defined. In this case, DCI formats 0, 1A, 3, and 3A are defined to have the same message size in order to reduce the number of blind decoding, which will be described later. These DCI formats are i) DCI formats 0, 4, ii) DCI formats 1, 1A, 1B, 1C, 1D, 2, used for downlink scheduling assignment depending on the purpose of the control information to be transmitted. 2A, 2B, 2C, and iii) DCI formats 3 and 3A for power control commands.

In case of DCI format 0 used for uplink scheduling grant, a carrier indicator necessary for carrier aggregation to be described later, an offset used to distinguish DCI formats 0 and 1A (flag for format 0 / format 1A differentiation), A frequency hopping flag indicating whether frequency hopping is used in uplink PUSCH transmission, information on resource block assignment, modulation and coding scheme to be used for PUSCH transmission, and a modulation and coding scheme. ), A new data indicator used to empty the buffer for initial transmission in relation to the HARQ process, a TPC command for scheduled for PUSCH, and a cycle for demodulation reference signal (DMRS). Cyclic shift for DM RS and OCC index, UL index and channel quality information required for TDD operation r) request information (CSI request) and the like. Meanwhile, since DCI format 0 uses synchronous HARQ, it does not include a redundancy version like DCI formats related to downlink scheduling allocation. In the case of carrier offset, if cross carrier scheduling is not used, it is not included in the DCI format.

DCI format 4 is new in LTE-A Release 10 and is intended to support spatial multiplexing for uplink transmission in LTE-A. The DCI format 4 further includes information for spatial multiplexing as compared to the DCI format 0, and thus has a larger message size, and further includes additional control information in the control information included in the DCI format 0. That is, the DCI format 4 further includes a modulation and coding scheme for the second transport block, precoding information for multi-antenna transmission, and sounding reference signal request (SRS request) information. On the other hand, since DCI format 4 has a size larger than DCI format 0, it does not include an offset that distinguishes DCI format 0 and 1A.

DCI formats 1, 1A, 1B, 1C, 1D, 2, 2A, 2B, and 2C related to downlink scheduling allocation do not significantly support spatial multiplexing, but 1, 1A, 1B, 1C, 1D and 2, which support spatial multiplexing, It can be divided into 2A, 2B, and 2C.

DCI format 1C supports only frequency continuous allocation as a compact downlink allocation and does not include a carrier offset and a redundant version as compared to other formats.

DCI format 1A is a format for downlink scheduling and random access procedures. This includes an indicator indicating whether carrier offset, downlink distributed transmission is used, PDSCH resource allocation information, modulation and coding scheme, redundancy version, HARQ processor number to inform processor used for soft combining, HARQ The process may include a new data offset used to empty the buffer for initial transmission, a transmit power control command for PUCCH, and an uplink index required for TDD operation.

In the case of DCI format 1, most of the control information is similar to DCI format 1A. However, compared to DCI format 1A related to continuous resource allocation, DCI format 1 supports non-contiguous resource allocation. Therefore, DCI format 1 further includes a resource allocation header, so that control signaling overhead is somewhat increased as a trade-off of increasing flexibility of resource allocation.

DCI formats 1B and 1D are common in that precoding information is further included as compared with DCI format 1. DCI format 1B includes PMI verification and DCI format 1D includes downlink power offset information. The control information included in the DCI formats 1B and 1D is mostly identical to that of the DCI format 1A.

The DCI formats 2, 2A, 2B, and 2C basically include most of the control information included in the DCI format 1A, and further include information for spatial multiplexing. This includes the modulation and coding scheme, the new data offset, and the redundancy version for the second transport block.

DCI format 2 supports closed-loop spatial multiplexing, while 2A supports open-loop spatial multiplexing. Both contain precoding information. DCI format 2B supports dual layer spatial multiplexing combined with beamforming and further includes cyclic shift information for DMRS. DCI format 2C can be understood as an extension of DCI format 2B and supports public multiplexing up to eight layers.

DCI formats 3 and 3A may be used to supplement transmission power control information included in DCI formats for uplink scheduling grant and downlink scheduling assignment, that is, to support semi-persistent scheduling. . In the case of DCI format 3, 1 bit per terminal and 2 bit in 3A are used.

Any one of the above-described DCI formats may be transmitted through one PDCCH, and a plurality of PDCCHs may be transmitted in a control region. The terminal may monitor the plurality of PDCCHs.

PDCCH Processing

In transmitting the DCI on the PDCCH, a Cyclic Redundancy Check (CRC) is attached to the DCI, and in this process, a radio network temporary identifier (RNTI) is masked. Here, the RNTI may use different RNTIs according to the purpose of transmitting the DCI. Specifically, the P-RNTI is used for a paging message related to network initiated connection establishment, the RA-RNTI is used for random access, and the SI-RNTI is used for a system information block (SIB). Can be. In the case of unicast transmission, C-RNTI, which is a unique terminal identifier, may be used. DCI with CRC is coded with a predetermined code and then adjusted to the amount of resources used for transmission through rate-matching.

In the transmission of the PDCCH as described above, when the PDCCH is mapped to the REs for efficient processing, a control channel element (CCE), which is a continuous logical allocation unit, is used. The CCE is composed of 36 REs, which corresponds to 9 units in a resource element group (REG). The number of CCEs required for a specific PDCCH depends on the DCI payload, cell bandwidth, channel coding rate, etc., which are the size of control information. In more detail, the number of CCEs for a specific PDCCH may be defined according to the PDCCH format as shown in Table 1 below.

Table 1

PDCCH Format	CCE Count	REG Count	PDCCH Bits
0	One	9	72
One	2	18	144
2	4	36	288
3	8	72	576

As can be seen from Table 1, the number of CCEs varies according to the PDCCH format. For example, the transmitter may use the PDCCH format 0 and then adaptively use the PDCCH format by changing the PDCCH format to 2 when the channel condition worsens. have.

Blind decoding

As described above, the PDCCH may use any one of four formats, which is not known to the UE. Therefore, the UE needs to decode without knowing the PDCCH format, which is called blind decoding. However, since it is a heavy burden for the UE to decode all possible CCEs used for downlink for each PDCCH format, a search space is defined in consideration of the scheduler limitation and the number of decoding attempts.

That is, the search space is a set of candidate PDCCHs consisting of CCEs that the UE should attempt to decode on an aggregation level. Here, the aggregation level and the number of PDCCH candidates may be defined as shown in Table 2 below.

TABLE 2

	Navigation		PDCCH Candidates
	Set level	Size (CCE)
Terminal specific	One	6	6
	2	12	6
	4	8	2
	8	16	2
common	4	16	4
	8	16	2

As shown in Table 2, since four aggregation levels exist, the terminal has a plurality of search spaces according to each aggregation level.

In addition, as shown in Table 2, the search space may be divided into a terminal specific search space and a common search space. The UE-specific discovery space is for specific UEs, and each UE monitors the UE-specific discovery space (attempting to decode a PDCCH candidate set according to a possible DCI format) to check the RNTI and CRC masked on the PDCCH. Control information can be obtained.

The common search space is for a case where a plurality of terminals or all terminals need to receive the PDCCH, such as dynamic scheduling or paging message for system information. However, the common search space may be used for a specific terminal for resource management. In addition, the common search space may overlap with the terminal specific search space.

4 is a diagram illustrating a structure of an uplink subframe. The uplink subframe may be divided into a control region and a data region in the frequency domain. A physical uplink control channel (PUCCH) including uplink control information is allocated to the control region. In the data area, a physical uplink shared channel (PUSCH) including user data is allocated. In order to maintain a single carrier characteristic, one UE does not simultaneously transmit a PUCCH and a PUSCH. PUCCH for one UE is allocated to an RB pair in a subframe. Resource blocks belonging to a resource block pair occupy different subcarriers for two slots. This is called a resource block pair allocated to the PUCCH is frequency-hopped at the slot boundary.

Physical Uplink Control Channel (PUCCH)

The uplink control information (UCI) transmitted through the PUCCH may include a scheduling request (SR), HARQ ACK / NACK information, and downlink channel measurement information.

HARQ ACK / NACK information may be generated according to whether the decoding of the downlink data packet on the PDSCH is successful. In a conventional wireless communication system, one bit is transmitted as ACK / NACK information for downlink single codeword transmission, and two bits are transmitted as ACK / NACK information for downlink 2 codeword transmission.

The channel measurement information refers to feedback information related to a multiple input multiple output (MIMO) scheme, and includes channel quality indicator (CQI), precoding matrix index (PMI), and rank indicator (Rank). Indicator (RI). These channel measurement information may be collectively expressed as CQI. 20 bits per subframe may be used for transmission of the CQI.

PUCCH may be modulated using Binary Phase Shift Keying (BPSK) and Quadrature Phase Shift Keying (QPSK). Control information of a plurality of terminals may be transmitted through the PUCCH, and a constant amplitude zero autocorrelation (CAZAC) sequence having a length of 12 when code division multiplexing (CDM) is performed to distinguish signals of the terminals Mainly used. Since the CAZAC sequence has a characteristic of maintaining a constant amplitude in the time domain and the frequency domain, the coverage is reduced by reducing the Peak-to-Average Power Ratio (PAPR) or the Cubic Metric (CM) of the UE. It has a suitable property to increase. In addition, ACK / NACK information for downlink data transmission transmitted through the PUCCH is covered using an orthogonal sequence or an orthogonal cover (OC).

In addition, the control information transmitted on the PUCCH can be distinguished using a cyclically shifted sequence having different cyclic shift (CS) values. The cyclically shifted sequence may be generated by cyclically shifting a base sequence by a specific cyclic shift amount. The specific CS amount is indicated by the cyclic shift index (CS index). The number of cyclic shifts available may vary depending on the delay spread of the channel. Various kinds of sequences may be used as the base sequence, and the above-described CAZAC sequence is one example.

In addition, the amount of control information that the UE can transmit in one subframe is based on the number of SC-FDMA symbols available for transmission of control information (ie, RS transmission for coherent detection of PUCCH). SC-FDMA symbols except for the SC-FDMA symbol used).

PUCCH format 1 is used for single transmission of SR. In the case of SR transmission alone, an unmodulated waveform is applied, which will be described later in detail.

PUCCH format 1a or 1b is used for transmission of HARQ ACK / NACK. When HARQ ACK / NACK is transmitted alone in any subframe, PUCCH format 1a or 1b may be used. Alternatively, HARQ ACK / NACK and SR may be transmitted in the same subframe using PUCCH format 1a or 1b.

PUCCH format 2 is used for transmission of CQI, and PUCCH format 2a or 2b is used for transmission of CQI and HARQ ACK / NACK. In the case of an extended CP, PUCCH format 2 may be used for transmission of CQI and HARQ ACK / NACK.

5 shows a form in which PUCCH formats are mapped to PUCCH regions in an uplink physical resource block. In Figure 5

Denotes the number of resource blocks in uplink, and 0, 1, ...

Is the number of the physical resource block. Basically, the PUCCH is mapped to both edges of the uplink frequency block. As shown in FIG. 6, PUCCH format 2 / 2a / 2b is mapped to a PUCCH region represented by m = 0,1, which means that the PUCCH format 2 / 2a / 2b is located at a band-edge. It can be expressed as being mapped to blocks. In addition, PUCCH format 2 / 2a / 2b and PUCCH format 1 / 1a / 1b may be mixed together in a PUCCH region indicated by m = 2. Next, the PUCCH format 1 / 1a / 1b may be mapped to the PUCCH region represented by m = 3, 4, 5. Number of PUCCH RBs available by PUCCH format 2 / 2a / 2b

) May be indicated to terminals in a cell by broadcasting signaling.

PUCCH Resources

The UE allocates PUCCH resources for transmission of uplink link control information (UCI) from the base station (BS) by an explicit method or an implicit method through higher layer signaling.

In the case of ACK / NACK, a plurality of PUCCH resource candidates may be configured by a higher layer for the UE, and which PUCCH resource is used, may be determined in an implicit manner. For example, the UE may transmit an ACK / NACK for the corresponding data unit through a PUCCH resource that is implicitly determined by the PDCCH resource that receives the PDSCH from the BS and carries scheduling information for the PDSCH.

6 shows an example of determining a PUCCH resource for ACK / NACK.

In the LTE system, the PUCCH resources for ACK / NACK are not pre-allocated to each UE, and a plurality of PUCCH resources are divided and used every time by a plurality of UEs in a cell. Specifically, the PUCCH resource used by the UE to transmit ACK / NACK is determined in an implicit manner based on the PDCCH carrying scheduling information for the PDSCH carrying the corresponding downlink data. The entire region in which the PDCCH is transmitted in each DL subframe consists of a plurality of control channel elements (CCEs), and the PDCCH transmitted to the UE consists of one or more CCEs. The CCE includes a plurality (eg, nine) Resource Element Groups (REGs). One REG is composed of four neighboring REs in the state excluding a reference signal (RS). The UE uses an implicit PUCCH resource derived or calculated by a function of a specific CCE index (eg, the first or lowest CCE index) among the indexes of CCEs constituting the PDCCH received by the UE. Send ACK / NACK.

Referring to FIG. 6, each PUCCH resource index corresponds to a PUCCH resource for ACK / NACK. As shown in FIG. 6, when it is assumed that scheduling information for a PDSCH is transmitted to a UE through a PDCCH configured with 4 to 6 CCEs, the UE derives or calculates the index from the 4th CCE, which is the lowest CCE constituting the PDCCH. The ACK / NACK is transmitted to the BS through the PUCCH, for example, the 4th PUCCH. FIG. 6 illustrates a case in which up to M ′ CCEs exist in a DL and up to M PUCCHs exist in a UL. M 'may be M, but M' and M may be designed differently, and mapping of CCE and PUCCH resources may overlap.

For example, the PUCCH resource index may be determined as follows.

Equation 1

Here, n (1) PUCCH represents a PUCCH resource index for ACK / NACK transmission, and N (1) PUCCH represents a signaling value received from an upper layer. nCCE may indicate the smallest value among the CCE indexes used for PDCCH transmission. Looking at the PUCCH in more detail as follows.

PUCCH Channel Structure

The PUCCH formats 1a and 1b will be described first.

In the PUCCH format 1a / 1b, a symbol modulated using a BPSK or QPSK modulation scheme is multiply multiplied by a CAZAC sequence having a length of 12. For example, the result of multiplying modulation symbol d (0) by length CAZAC sequence r (n) (n = 0, 1, 2, ..., N-1) is y (0), y (1). ), y (2), ..., y (N-1). The y (0), ..., y (N-1) symbols may be referred to as a block of symbols. After multiplying the CAZAC sequence by the modulation symbol, block-wise spreading using an orthogonal sequence is applied.

A Hadamard sequence of length 4 is used for general ACK / NACK information, and a Discrete Fourier Transform (DFT) sequence of length 3 is used for shortened ACK / NACK information and a reference signal. A Hadamard sequence of length 2 is used for the reference signal in the case of an extended CP.

7 shows a structure of an ACK / NACK channel in case of a normal CP. 7 exemplarily shows a PUCCH channel structure for HARQ ACK / NACK transmission without CQI. A reference signal RS is carried on three consecutive SC-FDMA symbols in the middle of seven SC-FDMA symbols included in one slot, and an ACK / NACK signal is carried on the remaining four SC-FDMA symbols. Meanwhile, in the case of an extended CP, RS may be carried on two consecutive symbols in the middle. The number and position of symbols used for the RS may vary depending on the control channel, and the number and position of symbols used for the ACK / NACK signal associated therewith may also be changed accordingly.

1 bit and 2 bit acknowledgment information (unscrambled state) may be represented by one HARQ ACK / NACK modulation symbol using BPSK and QPSK modulation techniques, respectively. The acknowledgment (ACK) may be encoded as '1', and the negative acknowledgment (NACK) may be encoded as '0'.

When transmitting control signals in the allocated band, two-dimensional spreading is applied to increase the multiplexing capacity. That is, frequency domain spreading and time domain spreading are simultaneously applied to increase the number of terminals or control channels that can be multiplexed. In order to spread the ACK / NACK signal in the frequency domain, a frequency domain sequence is used as the base sequence. As the frequency domain sequence, a Zadoff-Chu (ZC) sequence, which is one of the CAZAC sequences, may be used. For example, different cyclic shifts (CS) are applied to a ZC sequence, which is a basic sequence, so that multiplexing of different terminals or different control channels may be applied. The number of CS resources supported in an SC-FDMA symbol for PUCCH RBs for HARQ ACK / NACK transmission is determined by a cell-specific higher-layer signaling parameter (

),

∈ {1, 2, 3} represents 12, 6 or 4 shift, respectively.

The frequency domain spread ACK / NACK signal is spread in the time domain using an orthogonal spreading code. As the orthogonal spreading code, a Walsh-Hadamard sequence or a DFT sequence may be used. For example, the ACK / NACK signal may be spread using orthogonal sequences w0, w1, w2, and w3 of length 4 for four symbols. RS is also spread through an orthogonal sequence of length 3 or length 2. This is called orthogonal covering (OC).

A plurality of terminals may be multiplexed using a Code Division Multiplex (CDM) scheme using the CS resource in the frequency domain and the OC resource in the time domain as described above. That is, ACK / NACK information and RS of a large number of terminals may be multiplexed on the same PUCCH RB.

For this time domain spreading CDM, the number of spreading codes supported for ACK / NACK information is limited by the number of RS symbols. That is, since the number of RS transmission SC-FDMA symbols is smaller than the number of ACK / NACK information transmission SC-FDMA symbols, the multiplexing capacity of the RS is smaller than that of the ACK / NACK information. For example, in case of a normal CP, ACK / NACK information may be transmitted in four symbols. For the ACK / NACK information, three orthogonal spreading codes are used instead of four, which means that the number of RS transmission symbols is three. This is because only three orthogonal spreading codes can be used for the RS.

Examples of orthogonal sequences used for spreading ACK / NACK information are shown in Tables 3 and 4. Table 3 shows the sequences for length 4 symbols and Table 4 shows the sequences for length 3 symbols. The sequence for the length 4 symbol is used in the PUCCH format 1 / 1a / 1b of the general subframe configuration. In the subframe configuration, a sequence of 4 symbols in length is applied in the first slot and 3 symbols in length in the second slot, taking into account a case in which a Sounding Reference Signal (SRS) is transmitted in the last symbol of the second slot. The shortened PUCCH format 1 / 1a / 1b of the sequence may be applied.

TABLE 3

sequence index	{w (0), w (1), w (2), w (3)}
0	[+1 +1 +1 +1]
One	[+1 -1 +1 -1]
2	[+1 -1 -1 +1]

Table 4

sequence index	(0), w (1), w (2), w (3)}
0	[1 1 1]
One	[One ]
2	[One ]

Meanwhile, an example of an orthogonal sequence used for spreading RS of an ACK / NACK channel is shown in Table 5.

Table 5

sequence index	normal CP	extended CP
0	[1 1 1]	[1 1]
One	[One ]	[1 -1]
2	[One ]	N / A

In the case where three symbols in one slot are used for RS transmission and four symbols are used for ACK / NACK information transmission in a subframe of a general CP, for example, six cyclic shifts (CS) and If three orthogonal cover (OC) resources are available in the time domain, HARQ acknowledgments from a total of 18 different terminals can be multiplexed within one PUCCH RB. If two symbols in one slot are used for RS transmission and four symbols are used for ACK / NACK information transmission in a subframe of an extended CP, for example, six cyclic shifts in the frequency domain ( If two orthogonal cover (OC) resources can be used in the CS) and the time domain, HARQ acknowledgments from a total of 12 different terminals can be multiplexed within one PUCCH RB.

Next, PUCCH format 1 will be described. The scheduling request SR is transmitted in such a manner that the terminal requests or does not request to be scheduled. The SR channel reuses the ACK / NACK channel structure in PUCCH formats 1a / 1b and is configured in an OOK (On-Off Keying) scheme based on the ACK / NACK channel design. Reference signals are not transmitted in the SR channel. Therefore, a sequence of length 7 is used for a general CP, and a sequence of length 6 is used for an extended CP. Different cyclic shifts or orthogonal covers may be assigned for SR and ACK / NACK. That is, for positive SR transmission, the UE transmits HARQ ACK / NACK through resources allocated for SR. In order to transmit a negative SR, the UE transmits HARQ ACK / NACK through a resource allocated for ACK / NACK.

Next, the PUCCH format 2 / 2a / 2b will be described. PUCCH format 2 / 2a / 2b is a control channel for transmitting channel measurement feedback (CQI, PMI, RI).

The reporting period of the channel measurement feedback (hereinafter, collectively referred to as CQI information) and the frequency unit (or frequency resolution) to be measured may be controlled by the base station. Periodic and aperiodic CQI reporting can be supported in the time domain. PUCCH format 2 may be used only for periodic reporting and PUSCH may be used for aperiodic reporting. In the case of aperiodic reporting, the base station may instruct the terminal to transmit an individual CQI report on a resource scheduled for uplink data transmission.

8 shows a structure of a CQI channel in the case of a normal CP. Of the SC-FDMA symbols 0 to 6 of one slot, SC-FDMA symbols 1 and 5 (second and sixth symbols) are used for demodulation reference signal (DMRS) transmission, and CQI in the remaining SC-FDMA symbols. Information can be transmitted. Meanwhile, in the case of an extended CP, one SC-FDMA symbol (SC-FDMA symbol 3) is used for DMRS transmission.

In the PUCCH format 2 / 2a / 2b, modulation by a CAZAC sequence is supported, and a QPSK modulated symbol is multiplied by a length 12 CAZAC sequence. The cyclic shift (CS) of the sequence is changed between symbol and slot. Orthogonal covering is used for DMRS.

Reference signal (DMRS) is carried on two SC-FDMA symbols spaced by three SC-FDMA symbol intervals among seven SC-FDMA symbols included in one slot, and CQI information is carried on the remaining five SC-FDMA symbols. Two RSs are used in one slot to support a high speed terminal. In addition, each terminal is distinguished using a cyclic shift (CS) sequence. The CQI information symbols are modulated and transmitted throughout the SC-FDMA symbol, and the SC-FDMA symbol is composed of one sequence. That is, the terminal modulates and transmits the CQI in each sequence.

The number of symbols that can be transmitted in one TTI is 10, and modulation of CQI information is determined up to QPSK. When QPSK mapping is used for an SC-FDMA symbol, a 2-bit CQI value may be carried, and thus a 10-bit CQI value may be loaded in one slot. Therefore, a CQI value of up to 20 bits can be loaded in one subframe. A frequency domain spread code is used to spread the CQI information in the frequency domain.

As the frequency domain spreading code, a length-12 CAZAC sequence (eg, a ZC sequence) may be used. Each control channel may be distinguished by applying a CAZAC sequence having a different cyclic shift value. IFFT is performed on the frequency domain spread CQI information.

12 different terminals may be orthogonally multiplexed on the same PUCCH RB by means of 12 equally spaced cyclic shifts. The DMRS sequence on SC-FDMA symbol 1 and 5 (on SC-FDMA symbol 3 in extended CP case) in the general CP case is similar to the CQI signal sequence on the frequency domain but no modulation such as CQI information is applied. UE is a PUCCH resource index (

May be semi-statically configured by higher layer signaling to periodically report different CQI, PMI, and RI types on the PUCCH resource indicated by h). Where the PUCCH resource index (

) Is information indicating a PUCCH region used for PUCCH format 2 / 2a / 2b transmission and a cyclic shift (CS) value to be used.

Next, the enhanced-PUCCH (e-PUCCH) format will be described. The e-PUCCH may correspond to PUCCH format 3 of the LTE-A system. Block spreading can be applied to ACK / NACK transmission using PUCCH format 3.

Unlike the conventional PUCCH format 1 series or 2 series, the block spreading scheme modulates control signal transmission using the SC-FDMA scheme. As shown in FIG. 9, a symbol sequence may be spread and transmitted on a time domain using an orthogonal cover code (OCC). By using the OCC, control signals of a plurality of terminals may be multiplexed on the same RB. In the case of the above-described PUCCH format 2, one symbol sequence is transmitted over a time domain and control signals of a plurality of terminals are multiplexed using a cyclic shift (CS) of a CAZAC sequence, whereas a block spread based PUCCH format (for example, In the case of PUCCH format 3), one symbol sequence is transmitted over a frequency domain, and control signals of a plurality of terminals are multiplexed using time-domain spreading using OCC.

In FIG. 9 (a), four SC-FDMA symbols (i.e., data portions) are generated by using an OCC having a length = 4 (or spreading factor (SF) = 4) in one symbol sequence for one slot. An example of transmission is shown. In this case, three RS symbols (ie, RS portions) may be used during one slot.

Alternatively, FIG. 9 (b) shows an example of generating and transmitting five SC-FDMA symbols (i.e., data portions) by using an OCC having a length = 5 (or SF = 5) in one symbol sequence during one slot. . In this case, two RS symbols may be used for one slot.

In the example of FIG. 9, an RS symbol may be generated from a CAZAC sequence to which a specific cyclic shift value is applied, and may be transmitted in a form in which a predetermined OCC is applied (or multiplied) over a plurality of RS symbols. In addition, in the example of FIG. 9, if 12 modulation symbols are used for each OFDM symbol (or SC-FDMA symbol), and each modulation symbol is generated by QPSK, the maximum number of bits that can be transmitted in one slot is shown. Becomes 12x2 = 24 bits. Therefore, the number of bits that can be transmitted in two slots is a total of 48 bits. As described above, when the block spread type PUCCH channel structure is used, control information having an extended size can be transmitted as compared to the PUCCH format 1 series and 2 series.

Reference Signal (RS)

When transmitting a packet in a wireless communication system, since the transmitted packet is transmitted through a wireless channel, signal distortion may occur during transmission. In order to correctly receive the distorted signal at the receiving end, the distortion must be corrected in the received signal using the channel information. In order to find out the channel information, a method of transmitting the signal known to both the transmitting side and the receiving side, and finding the channel information with the distortion degree when the signal is received through the channel is mainly used. The signal is called a pilot signal or a reference signal.

When transmitting and receiving data using multiple antennas, it is necessary to know the channel condition between each transmitting antenna and the receiving antenna to receive the correct signal. Therefore, a separate reference signal must exist for each transmit antenna.

The downlink reference signal includes a common reference signal (CRS) shared by all terminals in a cell and a dedicated reference signal (DRS) only for a specific terminal. Such reference signals may provide information for channel estimation and demodulation.

The receiver (terminal) estimates the state of the channel from the CRS and feeds back indicators related to channel quality such as channel quality indicator (CQI), precoding matrix index (PMI), and / or rank indicator (RI) to the transmitter (base station). can do. The CRS may be called a cell-specific reference signal. Alternatively, RS related to feedback of Channel State Information (CSI) such as CQI / PMI / RI may be separately defined as CSI-RS.

Meanwhile, when demodulation of data on the PDSCH is required, the DRS may be transmitted through the corresponding RE. The UE may be instructed as to whether DRS is present from a higher layer and may be instructed that the DRS is valid only when the corresponding PDSCH is mapped. The DRS may also be called a UE-specific reference signal or a demodulation reference signal (DMRS).

FIG. 10 is a diagram illustrating a pattern in which CRSs and DRSs defined in an existing 3GPP LTE system (eg, Release-8) are mapped onto a downlink resource block pair (RB pair). A downlink resource block pair as a unit to which a reference signal is mapped may be expressed in units of 12 subcarriers in one subframe × frequency in time. That is, one resource block pair has 14 OFDM symbol lengths in the case of a general CP (Fig. 10 (a)) and 12 OFDM symbol lengths in the case of an extended CP (Fig. 10 (b)).

10 shows a position on a resource block pair of a reference signal in a system in which a base station supports four transmit antennas. In FIG. 10, resource elements RE denoted by '0', '1', '2' and '3' indicate positions of CRSs for antenna port indexes 0, 1, 2, and 3, respectively. Meanwhile, the resource element denoted as 'D' in FIG. 10 indicates the position of the DRS.

Sounding Reference Signal (SRS)

The sounding reference signal (SRS) is mainly used for frequency-selective scheduling on uplink by a base station measuring channel quality and is not associated with uplink data and / or control information transmission. Do not. However, the present invention is not limited thereto, and the SRS may be used for the purpose of improved power control or for supporting various start-up functions of terminals not recently scheduled. The start function may include, for example, an initial modulation and coding scheme (MCS), initial power control for data transmission, timing advance and frequency anti-selective scheduling (in the first slot of a subframe). Frequency resources are selectively allocated and may include pseudo-random hopping to other frequencies in the second slot).

In addition, the SRS may be used for downlink channel quality measurement under the assumption that the radio channel is reciprocal between uplink and downlink. This assumption is particularly valid in time division duplex (TDD) systems where uplink and downlink share the same frequency band and are distinguished in the time domain.

The subframe in which the SRS is transmitted by any terminal in the cell is indicated by cell-specific broadcast signaling. The 4-bit cell-specific 'SrsSubframeConfiguration' parameter represents 15 possible configurations of subframes in which an SRS can be transmitted within each radio frame. This configuration can provide flexibility to adjust SRS overhead according to network deployment scenarios. The configuration of the other (16th) of the parameter is to switch off the SRS transmission in the cell completely, for example, may be suitable for a cell serving mainly high speed terminals.

As shown in FIG. 11, the SRS is always transmitted on the last SC-FDMA symbol of the configured subframe. Therefore, the SRS and the demodulation reference signal (DMRS) are located on different SC-FDMA symbols. PUSCH data transmissions are not allowed on the SC-FDMA symbols designated for SRS transmissions, and therefore do not exceed approximately 7% even when the sounding overhead is highest (that is, when there is an SRS transmission symbol in every subframe). .

Each SRS symbol is generated by a base sequence (random sequence or Zadoff-Chu-based sequence set) for a given time unit and frequency band, and all terminals in a cell use the same base sequence. In this case, SRS transmissions from a plurality of terminals in a cell in the same time unit and the same frequency band are orthogonally distinguished by different cyclic shifts of a basic sequence allocated to the plurality of terminals. SRS sequences of different cells can be distinguished by assigning different base sequences from cell to cell, but orthogonality between different base sequences is not guaranteed.

Relay

The relay facilitates the service by extending the service area of the base station or installing in a shaded area. The terminal communicates with the base station or the relay. A terminal that communicates with a base station is referred to as a macro UE, and a terminal that communicates with a relay is referred to as a relay UE. The communication link between the base station and the macro terminal is referred to as a macro access link, and the communication link between the relay and the relay terminal is referred to as a relay access link. In addition, the communication link between the base station and the relay is referred to as a backhaul link.

Relays may be divided into L1 (layer 1) relays, L2 (layer 2) relays, and L3 (layer 3) relays according to how much they perform in multi hop transmission. In addition, the relay is an in-band connection in which the network-relay link and the network-terminal link share the same frequency band in the donor cell according to the network link, and the network-relay link in the donor cell. And network-terminal links may be divided into out-band connections using different frequency bands. In addition, the terminal may be divided into a transparent relay whose terminal does not know whether it is communicating through a relay and a non-transparent relay which knows whether the terminal communicates through the relay. have. In terms of mobility, relays are fixed relays that can be used to increase shadow area or cell coverage, nomadic relays that can be temporarily installed or moved randomly when users suddenly increase, or public transportation such as buses or trains. It can be divided into a mobile relay that can be mounted on.

12 shows an example of performing backhaul transmission using an MBSFN subframe. In in-band relay mode, the base station-relay link (ie, backhaul link) operates in the same frequency band as the relay-end link (ie, relay access link). In the case where a relay transmits a signal to a terminal while receiving a signal from a base station or vice versa, the relay transmitter and receiver cause interference with each other, so that the relay can simultaneously transmit and receive. To this end, the backhaul link and the relay access link are partitioned in a TDM manner. LTE-A configures a backhaul link in an MBSFN subframe to support measurement operation of a legacy LTE terminal existing in a relay zone (fake MBSFN method). If any subframe is signaled to the MBSFN subframe, the terminal receives only the control region (ctrl) of the corresponding subframe, and thus the relay may configure the backhaul link using the data region of the corresponding subframe.

Carrier merge

13 is a diagram for describing carrier aggregation. Prior to describing carrier aggregation, a concept of a cell introduced to manage radio resources in LTE-A will be described first. A cell may be understood as a combination of downlink resources and uplink resources. Here, the uplink resource is not an essential element, and thus, the cell may be composed of only the downlink resource or the downlink resource and the uplink resource. However, this is the definition in the current LTE-A Release 10 and vice versa, that is, the cell may be made up of uplink resources alone. The downlink resource may be referred to as a downlink component carrier (DL CC) and the uplink resource may be referred to as an uplink component carrier (UL CC). The DL CC and the UL CC may be represented by a carrier frequency, and the carrier frequency means a center frequency in a corresponding cell.

A cell may be classified into a primary cell (PCell) operating at a primary frequency and a secondary cell (SCell) operating at a secondary frequency. PCell and SCell may be collectively referred to as a serving cell. In the PCell, the terminal may perform an initial connection establishment (initial connection establishment) process, or the cell indicated in the connection reset process or handover process may be a PCell. That is, the PCell may be understood as a cell that is the center of control in a carrier aggregation environment to be described later. The UE may receive and transmit a PUCCH in its PCell. The SCell is configurable after the Radio Resource Control (RRC) connection is established and can be used to provide additional radio resources. In the carrier aggregation environment, the remaining serving cells except the PCell may be viewed as SCells. In the RRC_CONNECTED state, but the UE is not configured carrier aggregation or does not support carrier aggregation, there is only one serving cell consisting of a PCell. On the other hand, in the case of a terminal in the RRC_CONNECTED state and the carrier aggregation is configured, one or more serving cells exist, and all the serving cells include the PCell and the entire SCell. For a terminal supporting carrier aggregation, after the initial security activation process is initiated, the network may configure one or more SCells in addition to the PCell initially configured in the connection establishment process.

Hereinafter, carrier aggregation will be described with reference to FIG. 13. Carrier aggregation is a technology introduced to use a wider band in order to meet the demand for high speed data rates. Carrier aggregation may be defined as an aggregation of two or more component carriers (CCs) having different carrier frequencies. Referring to FIG. 13, FIG. 13A illustrates a subframe when one CC is used in an existing LTE system, and FIG. 13B illustrates a subframe when carrier aggregation is used. In FIG. 13B, three CCs of 20 MHz are used to support a total bandwidth of 60 MHz. Here, each CC may be continuous or may be non-continuous.

The terminal may simultaneously receive and monitor downlink data through a plurality of DL CCs. The linkage between each DL CC and UL CC may be indicated by system information. The DL CC / UL CC link may be fixed in the system or configured semi-statically. In addition, even if the entire system band is composed of N CCs, the frequency band that a specific UE can monitor / receive may be limited to M (<N) CCs. Various parameters for carrier aggregation may be set in a cell-specific, UE group-specific, or UE-specific manner.

14 is a diagram for describing cross carrier scheduling. Cross-carrier scheduling means, for example, including all downlink scheduling allocation information of another DL CC in a control region of one DL CC among a plurality of serving cells, or a DL CC of any one of a plurality of serving cells. This means that the control region includes all uplink scheduling grant information for the plurality of UL CCs linked with the DL CC.

First, a carrier indicator field (CIF) will be described.

As described above, the CIF may be included or not included in the DCI format transmitted through the PDCCH, and when included, it indicates that the cross carrier scheduling is applied. When cross carrier scheduling is not applied, downlink scheduling allocation information is valid on a DL CC through which current downlink scheduling allocation information is transmitted. The uplink scheduling grant is also valid for one UL CC linked with the DL CC through which the downlink scheduling assignment information is transmitted.

When cross carrier scheduling is applied, the CIF indicates a CC related to downlink scheduling allocation information transmitted through a PDCCH in one DL CC. For example, referring to FIG. 14, downlink allocation information about DL CC B and DL CC C, that is, information about PDSCH resources, is transmitted through a PDCCH in a control region on DL CC A. The UE monitors the DL CC A to know the resource region of the PDSCH and the corresponding CC through the CIF.

Whether CIF is included or not included in the PDCCH may be set semi-statically and may be UE-specific activated by higher layer signaling. When CIF is disabled, the PDCCH on a particular DL CC may allocate PDSCH resources on that same DL CC and allocate PUSCH resources on a UL CC linked to the particular DL CC. In this case, the same coding scheme, CCE-based resource mapping, DCI format, and the like as the existing PDCCH structure may be applied.

Meanwhile, when CIF is enabled, the PDCCH on a specific DL CC may allocate PDSCH / PUSCH resources on one DL / UL CC indicated by the CIF among a plurality of merged CCs. In this case, the CIF may be additionally defined in the existing PDCCH DCI format, may be defined as a fixed 3-bit field, or the CIF position may be fixed regardless of the DCI format size. In this case, the same coding scheme, CCE-based resource mapping, DCI format, and the like as the existing PDCCH structure may be applied.

Even if CIF exists, the base station can allocate a set of DL CC to monitor the PDCCH. Accordingly, the burden of blind decoding of the terminal can be reduced. The PDCCH monitoring CC set is a part of the total merged DL CCs and the UE may perform detection / decoding of the PDCCH only in the corresponding CC set. That is, in order to schedule PDSCH / PUSCH for the UE, the base station may transmit the PDCCH only on the PDCCH monitoring CC set. The PDCCH monitoring DL CC set may be configured as UE-specific or UE group-specific or cell-specific. For example, when three DL CCs are merged as in the example of FIG. 14, DL CC A may be set to the PDCCH monitoring DL CC. When CIF is deactivated, the PDCCH on each DL CC may only schedule PDSCH in DL CC A. On the other hand, when CIF is activated, the PDCCH on DL CC A may schedule not only DL CC A but also PDSCH on another DL CC. When DL CC A is set to PDCCH monitoring CC, PDSCCH is not transmitted to DL CC B and DL CC C.

In a system in which carrier aggregation is applied as described above, the UE may receive a plurality of PDSCHs through a plurality of downlink carriers, in which case, the UE performs ACK / NACK for each data in one subframe. There is a case that needs to be transmitted on the UL CC. When transmitting a plurality of ACK / NACK in one subframe using the PUCCH format 1a / 1b, high transmission power is required, the PAPR of the uplink transmission is increased and the base station of the terminal due to inefficient use of the transmission power amplifier The transmittable distance from can be reduced. In order to transmit a plurality of ACK / NACK through one PUCCH, ACK / NACK bundling or ACK / NACK multiplexing may be applied.

In addition, ACK / NACK information for a large number of downlink data and / or a large number of downlink data transmitted in a plurality of DL subframes in a TDD system according to carrier aggregation is transmitted through a PUCCH in one subframe. Cases may arise. In this case, if the number of ACK / NACK bits to be transmitted is larger than the number that can be supported by ACK / NACK bundling or multiplexing, the above methods cannot correctly transmit ACK / NACK information.

ACK / NACK Multiplexing Scheme

In the case of ACK / NACK multiplexing, the contents of the ACK / NACK response for a plurality of data units are in combination with one of the ACK / NACK unit and QPSK modulated symbols used in the actual ACK / NACK transmission. Can be identified. For example, it is assumed that one ACK / NACK unit carries two bits of information, and that a maximum of two data units are received. Here, it is assumed that the HARQ acknowledgment for each received data unit is represented by one ACK / NACK bit. In this case, the transmitting end that has transmitted the data can identify the ACK / NACK result as shown in Table 6 below.

Table 6

HARQ-ACK (0), HARQ-ACK (0)		b (0), b (1)
ACK, ACK		1,1
ACK, NACK / DTX		0,1
NACK / DTX, ACK		0,0
NACK / DTX, NACK		1,0
NACK, DTX		1,0
DTX, DTX	N / A	N / A

In Table 6, HARQ-ACK (i) (i = 0, 1) represents the ACK / NACK result for the data unit i. Since it is assumed that up to two data units (data unit 0 and data unit 1) are received as described above, in Table 6, the ACK / NACK result for data unit 0 is represented as HARQ-ACK (0), and data The ACK / NACK result for unit 1 is indicated by HARQ-ACK (1). In Table 6, DTX (Discontinuous Transmission) indicates that a data unit corresponding to HARQ-ACK (i) is not transmitted, or the receiving end does not detect the presence of a data unit corresponding to HARQ-ACK (i). It indicates that you cannot. Also,

Represents an ACK / NACK unit used for actual ACK / NACK transmission. If there are up to two ACK / NACK units,

And

It can be expressed as. Also, b (0) and b (1) indicate two bits transmitted by the selected ACK / NACK unit. The modulation symbol transmitted through the ACK / NACK unit is determined according to the b (0) and b (1) bits.

For example, if the receiving end has successfully received and decoded two data units (i.e., ACK and ACK of Table 5), the receiving end is an ACK / NACK unit.

To transmit two bits (1, 1). Or, when the receiving end receives two data units, the decoding (or detection) of the first data unit (ie, data unit 0 corresponding to HARQ-ACK (0)) fails and the second data unit (ie, If the decoding of the data unit 1 corresponding to the HARQ-ACK 1 is successful (i.e., in the case of NACK / DTX and ACK of Table 6 above), the receiving end is an ACK / NACK unit.

To transmit two bits (0,0).

As such, the combination of selection of the ACK / NACK unit and the actual bit contents of the transmitted ACK / NACK unit (i.e., in Table 6 above)

or

ACK for a plurality of data units using one ACK / NACK unit by linking or mapping one of the selection and a combination of b (0) and b (1) with the contents of the actual ACK / NACK. / NACK information can be transmitted. By extending the aforementioned principle of ACK / NACK multiplexing as it is, ACK / NACK multiplexing for more than 2 data units can be easily implemented.

In the ACK / NACK multiplexing scheme, if at least one ACK exists for all data units, NACK and DTX may not be distinguished (that is, represented as NACK / DTX in Table 6 above). NACK and DTX may be coupled). This is because all ACK / NACK states (that is, ACK / NACK hypotheses) that can occur when NACK and DTX are to be expressed separately can be reflected by a combination of an ACK / NACK unit and a QPSK modulated symbol. Because there is not. On the other hand, if no ACK exists for all data units (i.e., only NACK or DTX exists for all data units), only one of the HARQ-ACK (i) is definitely NACK (i.e. distinguished from DTX). One certain NACK case may be defined. In this case, the ACK / NACK unit corresponding to the data unit corresponding to one certain NACK may be reserved for transmitting signals of a plurality of ACK / NACKs.

Semi-persistent scheduling (SPS)

DL / UL semi-persistent scheduling (SPS) uses RRC (Radio Resource Control) signaling to specify to the UE which subframes should be transmitted / received (in subframe periods and offsets), and the actual SPS activation ( Activation and release are performed through the PDCCH. That is, even if the UE receives the SPS through RRC signaling, the UE does not immediately perform the SPS TX / RX but receives the PDCCH indicating activation (or reactivation) (that is, when the SPS C-RNTI detects the detected PDCCH). As a result, the SPS operation is performed. That is, when the SPS activation PDCCH is received, the frequency resource according to the RB allocation designated in the PDCCH is allocated, the modulation and coding rate according to the MCS information is applied, and TX / RX is performed with the subframe period and offset allocated by the RRC signaling. You can start doing it. Meanwhile, upon receiving the PDCCH indicating the release of the SPS, the UE stops TX / RX. When the suspended SPS TX / RX receives a PDCCH indicating activation (or reactivation), the SPS TX / RX may resume TX / RX again with the subframe period and offset allocated by RRC signaling according to the RB allocation, MCS, etc. specified in the PDCCH. have.

PDCCH format defined in 3GPP LTE currently defines various formats such as DCI format 0 for uplink and DCI formats 1, 1A, 1B, 1C, 1D, 2, 2A, 3, and 3A for downlink. Hopping flag, RB allocation, modulation coding scheme (MCS), redundancy version (RV), new data indicator (NDI), transmit power control (TPC), cyclic shift demodulation reference signal (DMRS), UL index, CQI ( Control information such as channel quality information) request, DL assignment index, HARQ process number, transmitted precoding matrix indicator (TPMI), and precoding matrix indicator (PMI) confirmation are transmitted in a selected combination.

More specifically, the use of the PDCCH for SPS scheduling activation / deactivation may be validated that the CRC of the DCI transmitted on the PDCCH is masked with the SPS C-RNTI, where NDI = 0 is set. At this time, in case of SPS activation, the combination of bit fields is set to 0 and used as a virtual CRC as shown in Table 7 below.

TABLE 7

	DCI format 0	DCI format 1 / 1A	DCI format	2 / 2A / 2B
TPC command for scheduled PUSCH	set to '00'	N / A	N / A
Cyclic shift DMRS	set to '000'	N / A	N / A
Modulation and coding scheme and redundancy version	MSB is set to '0'	N / A	N / A
HARQ process number	N / A	FDD: set to '000'	FDD: set to '000'
Modulation and coding scheme	N / A	MSB is set to '0'	For the enabled transport block: MSB is set to '0'
Redundancy version	N / A	set to '00'	For the enabled transport block: MSB is set to '00'

The virtual CRC checks whether or not the corresponding bit field value is a promised value when an error that cannot be checked by the CRC has additional error detection capability. If an error occurs in the DCI assigned to another UE, but a specific UE does not detect the error and misrecognizes it as its own SPS activation, one error causes a continuous problem because the resource is continuously used. Therefore, the use of virtual CRC prevents false detection of SPS.

In case of SPS release, set the value of bit field to use as virtual CRC as in the following table 8.

Table 8

	DCI format 0	DCI format 1A
TPC command for scheduled PUSCH	set to '00'	N / A
Cyclic shift DMRS	set to '000'	N / A
Modulation and coding scheme and redundancy version	set to '11111'	N / A
Resource block assignment and hopping resource allocation	Set to all '1's	N / A
HARQ process number	N / A	FDD: set to '000'
Modulation and coding scheme	N / A	set to '11111'
Redundancy version	N / A	set to '00'
Resource block assignment	N / A	set to all'1's

PUCCH Piggyback

In case of uplink transmission of the existing 3GPP LTE system (for example, Release-8) system, for efficient use of the power amplifier of the terminal, PAPR (Peak-to-Average Power Ratio) affecting the performance of the power amplifier The characteristics or the cubic metric (CM) characteristics are good to maintain a single carrier transmission. That is, in case of PUSCH transmission of the existing LTE system, data to be transmitted is maintained through DFT-precoding to maintain a single carrier property, and in case of PUCCH transmission, information is transmitted in a sequence having a single carrier property. Single carrier characteristics can be maintained. However, when the DFT-precoding data is allocated discontinuously on the frequency axis, or when the PUSCH and the PUCCH are simultaneously transmitted, this single carrier characteristic is broken.

Accordingly, when there is a PUSCH transmission in the same subframe as the PUCCH transmission, as shown in FIG. 15, uplink control information (UCI) information to be transmitted on the PUCCH is transmitted together with the data through the PUSCH in order to maintain a single carrier characteristic. .

As described above, since the existing LTE UE cannot simultaneously transmit the PUCCH and the PUSCH, the UCI (CQI / PMI, HARQ-ACK, RI, etc.) is multiplexed in the PUSCH region in the subframe in which the PUSCH is transmitted. For example, when CQI and / or PMI should be transmitted in a subframe allocated to transmit PUSCH, control information and data may be transmitted by multiplexing UL-SCH data and CQI / PMI before DFT-spreading. In this case, UL-SCH data performs rate-matching in consideration of CQI / PMI resources. In addition, control information such as HARQ ACK and RI may be multiplexed in the PUSCH region by puncturing UL-SCH data.

FIG. 16 is a diagram illustrating a multiplexing process of data and control information for uplink transmission.

As shown in FIG. 16, data information multiplexed together with the control information is transmitted to the transport block (hereinafter referred to as "TB") (a0, a1, ..., aA-1) to be transmitted in the uplink. After attaching the Cyclic Redundancy Check, it is divided into several code blocks (hereinafter referred to as "CBs") according to TB sizes, and CRCs for CBs are attached to several CBs. Channel coding is performed on this result. In addition, after the channel-coded data undergoes rate matching, combining between CBs is performed again, and the combined CBs are then multiplexed with a control signal.

Meanwhile, channel encoding is performed on the CQI / PMI (o0, o1, ..., oo-1) separately from the data. Channel coded CQI / PMI is multiplexed with data. The CQI / PMI information and the multiplexed data are input to the channel interleaver.

In addition, rank coding ([o0RI] or [o0RI o1RI]) is performed with channel coding separately from the data (S511). The channel-coded rank information is inserted into a part of the interleaved signal through a process such as puncturing.

In the case of ACK / NACK information ([o0ACK] or [o0 ACK o1 ACK]…), channel encoding is performed separately from data, CQI / PMI, and rank information. The channel-coded ACK / NACK information is inserted into a part of the interleaved signal through a process such as puncturing.

Meanwhile, the current LTE / LTE-A system uses a time-frequency resource of a licensed band. In the past, the number of communication terminals was not large, and even though a specific operator exclusively used the licensed band, frequency resources were sufficient. Recently, as ubiquitous computing is activated and the demand for high data rate increases, the demand for frequency resources is rapidly increased, and the problem of frequency resource shortage is realizing. Therefore, the interest in technology using the unlicensed band is increasing rapidly. Accordingly, the current LTE / LTE-A system operating based on the licensed band may be extended to use the unlicensed band. Hereinafter, based on the above description, the PDSCH and the licensed exempt band may be used. Methods for transmitting the PUSCH are described.

In the following description, for convenience of description, for example, as shown in FIG. 17, a system using two cells is assumed. It is assumed that one cell (eg, Pcell) corresponds to a licensed band and the other cell corresponds to an unlicensed band. However, this is for convenience of description and does not exclude that there may be more Scells (eg, LTE / LTE-A frequency band and / or unlicensed band) in the serving cell. Here, the Pcell and the Scell are mentioned in terms of carrier aggregation. In this case, the resources (PDSCH and / or PUSCH) on the unlicensed band may be indicated by the PDCCH of the Pcell. However, it should be noted that carrier aggregation is not all applied to the following descriptions, and PDSCH and / or PUSCH on an unlicensed band may be indicated by a PDCCH transmitted on an unlicensed band. In addition, even when the PDSCH and / or PUSCH on the unlicensed band are indicated by the PDCCH transmitted in the licensed band, the aforementioned cross carrier scheduling may not necessarily be applied as it is.

17, the base station may transmit a PDSCH on an unlicensed band, and the terminal may transmit a PUSCH on an unlicensed band. Here, the time unit used when transmitting the PDSCH and / or PUSCH on the unlicensed band may be the same as a subframe, a slot, an OFDM symbol, etc. of the licensed band, but is not necessarily limited thereto. In addition, in the context of the present invention, the unlicensed band may be used as a basic unit of a slot (which may be divided into a UL slot and a DL slot) in an LTE system on a time axis. This is because the carrier sensing timing may be related to the slots before and after the slot as described below.

Carrier sensing must be performed for signal transmission over the unlicensed band. Carrier sensing means to check whether the unlicensed band is used by another device when the base station or the terminal intends to use the unlicensed band. As a result of carrier sensing, when the unlicensed band is used by another device (Busy), the BS or the UE cannot transmit a signal and PDSCH / PUSCH can be transmitted when the unlicensed band is idle.

On the other hand, the following description, according to the embodiment

i) Scheduling after carrier sensing in PDSCH transmission on unlicensed band

ii) Postscheduled Carrier Sensing in PDSCH Transmission on Unlicensed Band

iii) PUSCH transmission on unlicensed band

iv) transmission of a preamble for synchronization acquisition in PDSCH / PUSCH transmission on an unlicensed band

This is explained sequentially. Here, i) to iv) are described on the premise of the OFDM scheme for convenience of description, but the OFDMA scheme may also be applied as described below.

Example  One

18 is a diagram for explaining PDSCH transmission in an unlicensed band according to an embodiment of the present invention.

In detail, FIG. 18 illustrates an example in which carrier sensing is first performed to transmit a PDSCH on an unlicensed band, and scheduling is performed for an unlicensed band when the unlicensed band is available as a result of the carrier sensing. It will be described in detail below.

The base station performs carrier sensing from the time before subframe n as shown in order to transmit the PDSCH in subframe n on the unlicensed band. Carrier sensing may be performed at specific intervals as shown in FIG. 18, which may be an OFDM symbol interval of a subframe. However, a shorter interval or longer interval than the OFDM symbol interval may be applied.

If carrier sensing is performed at a specific interval and it is determined that the unlicensed band is available at any time before subframe n, the PDSCH may be scheduled on the unlicensed band. This scheduling information may be transmitted on the PDCCH of the licensed band. Here, as shown in FIG. 18, if the time when the unlicensed band is available as a result of carrier sensing is earlier than the start point of the subframe in which the PDCCH is transmitted, that is, the start point of transmission of the subframe n, the subframe n is transmitted therefrom. Reservations must be made so that other devices that can use the unlicensed band up to the point of use cannot use the unlicensed band. In other words, if the base station is not transmitting any signal in the time interval indicated as reserved in FIG. 18, the other device performs carrier sensing to determine that it can use the unlicensed band and transmit the signal. Failure to transmit the PDSCH in subframe n results.

Therefore, the base station can solve this by transmitting a reservation signal in the time interval indicated as reserved in FIG. Here, the reservation signal may be a specific signal for notifying other devices wishing to use the unlicensed band that the base station uses the unlicensed band in the time interval. In other words, the reserved signal may be a promise that can be commonly recognized by devices that want to use the unlicensed band. In addition, the reservation signal may be a dummy signal including a specific sequence or a sequence generated by seeding a specific sequence. By transmitting the reservation signal in this way, the base station is scheduled without any problem even if the time when the unlicensed band is available as a result of carrier sensing is earlier than the start time of the subframe (time period corresponding to the subframe of the licensed band) to which the PDSCH is to be transmitted. PDSCH may be transmitted.

If carrier sensing is performed from the start of subframe n, unlike in FIG. 18, and if it is determined that the unlicensed band is available within a predetermined time period, the PDSCH is performed in a time interval shorter than one subframe time interval. The transmission must be made. In this case, a PDSCH having a reduced time length may be transmitted using a method such as rate matching used in the LTE / LTE-A system. The UE has a problem in that it is not possible to know a start time at which the PDSCH is transmitted. Therefore, the start time point at which the PDSCH is transmitted may be preset to a time (eg, 1st, 2nd, 3rd OFDM symbol) corresponding to a specific OFDM symbol of a subframe. The UE may find a start time point at which the PDSCH is transmitted by performing blind detection for these times.

On the other hand, unlike FIG. 18, the PDSCH may be scheduled using the R-PDCCH and the PDSCH transmission may be transmitted together with the backhaul subframe. In this case, there is a benefit in that the PDSCH transmission time is fixed.

Example  2

Embodiment 2 relates to a method of first performing scheduling and then performing carrier sensing to transmit a PDSCH on an unlicensed band. Unlike the first embodiment, since the PDSCH transmission is scheduled by performing carrier sensing without checking whether the unlicensed band is available, the PDSCH transmission may be delayed or the transmission may fail when the unlicensed band is not available. To solve this problem, PDSCH transmission may be set to a partial region of the time period of the subframe. This will be described with reference to FIG. 19.

19 is a diagram for explaining PDSCH transmission in an unlicensed band according to another embodiment of the present invention. The base station may schedule PDSCH transmission for a portion of the time interval of the unlicensed band, which corresponds to the time interval corresponding to the subframe length of the licensed band. Here, some sections may be half of the subframe, that is, the second slot, as shown in FIG. 19. However, the present invention is not necessarily limited thereto, and may be variously set from the n (0 <n <= 8) th OFDM symbol of the subframe to the last OFDM symbol of the subframe.

Subsequently, the base station starts carrier sensing from the start of the subframe to transmit the scheduled PDSCH. In this case, carrier sensing may be continuously performed at a specific interval (for example, OFDM symbol interval of a subframe) as described in the first embodiment. As a result of carrier sensing, if the unlicensed band is available (IDLE) before the scheduled start time of PDSCH transmission, the base station may transmit the PDSCH. However, if it is determined that the unlicensed band is available before the time when the PDSCH transmission is scheduled to start, it may be necessary to transmit the reserved signal to the unlicensed band. Specifically, if there is an interval between the start time of PDSCH transmission and the time at which the unlicensed band is available, other devices that want to use the unlicensed band may use the unlicensed band at this interval and thus the PDSCH transmission may fail. Therefore, a reservation signal as described in Embodiment 1, i.e., a specific signal or dummy signal for notifying other devices that want to use the unlicensed band at the interval (time interval) to notify the unlicensed band. By transmitting, the PDSCH can be transmitted stably. In addition, the reservation signal may be generated by duplicating the front part or the rear part of the scheduled PDSCH (cyclic shift method).

Since the MCS of the PDSCH transmitted in the second slot can be calculated from the MCS indicated by the PDCCH, no additional information may be needed. Of course, it may directly inform the MCS of the PDSCH transmitted in the second slot. Alternatively, the DCI of the PDCCH may include an MCS for one subframe and an MCS for one subframe half (one slot). The UE may determine by blind decoding whether it is one subframe or half of a subframe.

Alternatively, in order to increase the accuracy of demodulation, a signal (for example, preamble or sequence) that can inform the PDSCH start position transmitted in the unlicensed band may be transmitted. Such a signal may be masked with a UE ID or a preamble sequence generated based on the UE identifier. This method is advantageous for the transmission method immediately after the CS. For example, if the unlicensed band is available in the third OFDM symbol as a result of carrier sensing, the PDSCH is transmitted by transmitting a sequence or preamble in the fourth OFDM symbol. However, when the length of the transmitted PDSCH is variable, there is a disadvantage in that MCS is inferred, but the resource utilization rate can be increased.

Alternatively, subframes may be divided into smaller units (eg, OFDM 2 symbol bundles) to transmit PDSCHs in units of 12, 10, 8, and 7 OFDM symbol lengths, and MCS may be calculated and inferred or signaled separately.

On the other hand, unlike described in FIG. 19, if it is determined that the unlicensed band is available after the carrier sensing without fixing the transmission start time of the PDSCH to a specific time point, the PDSCH may be transmitted with a minimum or zero back off time. However, in this case, since it is difficult for the UE to know the transmission start time of the PDSCH and it is difficult to calculate the MCS, it is necessary to additionally inform the information.

Alternatively, the transmission start time of the PDSCH may be semi-statically set. For example, if the PDSCH is set to start with symbol n as an upper layer signal (RRC signal), carrier sensing may be performed before symbol n. In this case, if the unlicensed band is available (IDLE) as a result of carrier sensing, the PDSCH may be transmitted in symbol n. If the time when the unlicensed band is available is before symbol n, the above-described method of transmitting the reserved signal may be used. Another method is to set up a transmission waiting counter, reduce the value of the counter after a unit time and transmit it when it reaches 0. If the other device starts transmitting before 0, PDSCH transmission is performed. The method of giving up may apply. The scheduler may set the PDSCH transmission start position differently according to the success rate of carrier sensing.

In addition, the length of the scheduled PDSCH may be variably operated. In this case, information such as a start time, a length, and an end time of the PDSCH needs to be informed, and this information can be transmitted using some fields of the PDCCH. Alternatively, the preamble may be transmitted to inform the start time of the PDSCH while also transmitting length information. This may be useful when the unlicensed band is synchronized with the licensed band even though the unlicensed band is operated according to the subframe and slot structure of the licensed band.

As described above, since the PDSCH transmission is scheduled on the unlicensed band before performing the carrier sensing, if the unlicensed band cannot be continuously used as a result of the carrier sensing, the finally scheduled PDSCH transmission may fail. . When the UE receives the PDCCH but does not receive the PDSCH in the unlicensed band, the UE may know that the PDSCH has not been received, but may decode another signal instead of the PDSCH not transmitted. Accordingly, the base station may instruct the terminal to discard information stored in the buffer for the region previously scheduled for the PDSCH when the PDSCH transmission fails due to the unlicensed band. This indication may be transmitted on the PDCCH of the next subframe or may be included in the PDCCH after the k subframe. Alternatively, the signal may be transmitted using a signal other than the PDCCH (eg, another physical channel, higher layer signaling, etc.).

20 shows that a PDSCH of an unlicensed band unlicensed band is indicated by a PDCCH on an unlicensed band, rather than a PDCCH of a licensed band. That is, as shown in FIG. 20, the PDCCH including the PDSCH and scheduling information of the PDSCH may be transmitted from the time when the unlicensed band is available (or after a predetermined back off time) after carrier sensing.

FIG. 21 is a diagram illustrating slots in which PDSCHs are transmitted according to a time point when an unlicensed band is available by performing carrier sensing on an unlicensed band. Referring to FIG. 21 (a), when the time period when the unlicensed band is available is more than a predetermined OFDM symbol from the first OFDM symbol of the subframe, it can be seen that the transmission of the PDSCH is transmitted on the second slot of the subframe. On the contrary, in FIG. 21B, the PDSCH is transmitted in both the first slot and the second slot because the time when the unlicensed band is available is less than a predetermined OFDM symbol. Here, the predetermined OFDM symbol may be variously set to 2, 3 OFDM symbols, or the like, and the carrier sensing unit may be a reference instead of the OFDM symbol.

Example  3

Embodiment 3 relates to a method of transmitting a PUSCH on an unlicensed band. This will be described with reference to FIG. 22.

Referring to FIG. 22, it can be seen that a PDCCH transmitted in subframe n of a licensed band transmits a PUSCH in a time period corresponding to subframe n + 4 of a licensed band in an unlicensed band. For transmission of the scheduled PUSCH, the UE may perform carrier sensing from the start of subframe n + 4. If it is determined that the unlicensed band is available as a result of carrier sensing, the UE may transmit a PUSCH on the unlicensed band. Here, when the time point at which it is determined that the unlicensed band is available as a result of carrier sensing is earlier than the time point at which PUSCH transmission is started, the reservation signal described above for the reserved period may be transmitted. 22 is one of various PUSCH transmission methods, and descriptions for transmitting a PDSCH on an unlicensed band, such as a carrier sensing time point, a PUSCH transmission length, an MCS, and the like, may apply mutatis mutandis.

Meanwhile, the resource for PUSCH transmission may be reserved as a specific signal such as an uplink grant before several subframes while maintaining a regulation related to transmission in an unlicensed band. That is, the uplink grant enables the PUSCH to be transmitted in a specific subframe, slot, or OFDM symbol. For example, when operating on a slot basis, a carrier merge is received at the first slot or just before the first slot of a subframe coming after n + 4 (if the previous n + 3 subframe is downlink). For transmission, part of the last OFDM symbol or subframe may be a reduced length subframe that cannot be transmitted due to carrier sensing, or if the n + 3 subframe is for uplink transmission, the last OFDM symbol or carrier The PUSCH should be transmitted except for the interval corresponding to the detection.) If the unlicensed band is available (IDLE), the PUSCH is transmitted.

Alternatively, when receiving an uplink grant and performing carrier sensing, if the unlicensed band is available (IDLE), it is transmitted after a predetermined time (Random Back-off time). However, an upper limit and a lower limit of the random back off time are designated and one value may be selected therebetween. For example, instead of always fixing to n + 4, it gives the freedom to transmit at some specified time, such as n + 3 and n + 5. By doing so, it is possible to divide the resource sharing with the terminal or other system equipment evenly. For example, set the random backoff value to 4 to 6 and have one of 4, 5, and 6 values.

Example  4

Embodiment 4 relates to transmitting a preamble for synchronization acquisition in a time interval from when the unlicensed band becomes available as a result of carrier sensing and before the PDSCH or PUSCH is transmitted, as described with reference to FIGS. 24 to 26. Here, FIGS. 24 to 26 illustrate a case in which a base station transmits a PDSCH on an unlicensed band, but is not necessarily limited thereto, and in each case of the above-described embodiments 1 to 3, there is no conflict Can be applied. In addition, the preamble may be a preamble sequence masked with a UE identifier or a preamble sequence generated based on the UE identifier, as mentioned in Embodiment 2 above.

24 is a diagram for explaining preamble transmission in PDSCH transmission in an unlicensed band according to an embodiment of the present invention.

Referring to FIG. 24, it can be seen that the preamble is transmitted before the reservation signal. Specifically, the base station performs carrier sensing in order to determine whether the unlicensed band is available in subframe n-1. When the unlicensed band is available as a result of the carrier sensing, the base station may transmit the preamble after having a predetermined back off time. A reservation signal may be transmitted as shown for the time until the PDSCH is transmitted following the preamble transmission.

In this case, the preamble transmitted in advance of the reservation signal may serve to inform the terminal that transmission of the reservation signal is started. In addition, the preamble also performs the function of the reservation signal. That is, as mentioned above, the reserved signal means that other devices that want to use the unlicensed band from the time when the unlicensed band becomes available until the PDSCH is transmitted transmit a dummy signal or the like so as not to use the unlicensed band. This means that the transmission of the preamble also serves to prevent other devices from using the unlicensed band.

In this way, the base station can secure the resources for transmitting the PDSCH on the unlicensed band by transmitting the reservation signal continuously in the preamble transmission. The resources in the unlicensed band secured here are the number of subframes corresponding to the transmission opportunity (more precisely the resources in the unlicensed band corresponding to the number of subframes in the licensed band used by the base station corresponding to the transmission opportunity). Can be. 24 exemplarily shows that the transmission opportunity is set to three. Although the transmitted preamble is for synchronization of the reservation signal, the terminal may acquire synchronization for PDSCH transmission by using the position of the preamble, the duration of the reservation signal, and the boundary of the reception subframe.

In the case of FIG. 24, although the reservation signal is shown to be transmitted, the licensed band used by the base station at the time when it is determined that the unlicensed band is available by performing carrier sensing, as described in the above embodiments. In the case of either the subframe boundary or the slot boundary, the transmission of the reservation signal is unnecessary and may be omitted. In addition, transmission of the PDSCH on the unlicensed band may be scheduled before carrier sensing or scheduled after carrier sensing, and a detailed description thereof will be replaced with the description of Embodiments 1 and 2. FIG.

Scheduling information for the PDSCH transmitted on the unlicensed band may be delivered to the terminal by the PDCCH transmitted on the licensed band as described above, or unlike the illustrated in FIG. 24, transmitted on the unlicensed band via the PDCCH. May be If the preamble includes necessary scheduling information other than the identifier of the terminal receiving the PDSCH, the preamble may be operated in a manner that does not receive the scheduling information for the unlicensed band through the PDCCH.

FIG. 25 is a diagram for explaining that a preamble is transmitted after a reservation signal transmission in a PDSCH transmission in an unlicensed band according to an embodiment of the present invention. In FIG. 25 (a), the preamble is transmitted after the reservation signal transmission, and the preamble is transmitted at the subframe start timing of the licensed band. In FIG. 25 (b), the preamble is transmitted to be completed at the subframe start timing of the licensed band. Indicates. That is, in FIGs. 25A and 25B, the preamble is transmitted at the timing corresponding to the subframe boundary of the licensed band.

In this case, transmission of the preamble may be used for synchronization acquisition of the PDSCH to be transmitted or subframe synchronization acquisition of the licensed band. That is, from the terminal's point of view, when the preamble is received, the PDSCH is soon to be transmitted, so that the PDSCH reception timing can be accurately known.

Meanwhile, in FIG. 25, the transmission of the preamble is transmitted at a timing corresponding to the subframe boundary of the licensed band. Alternatively, the preamble may be transmitted at the slot boundary. That is, as described above with reference to FIG. 19, when the PDSCH transmission is performed by the slot unit in the unlicensed band, the preamble may be transmitted at the slot boundary. If the unlicensed band is not divided into subframes or slots of the licensed band and used in an arbitrary time interval unit, the transmission of the preamble is performed to obtain synchronization for PDSCH transmission for the arbitrary time interval. May be used.

In FIG. 26, the preamble is transmitted twice before and after transmission of the reservation signal. That is, in FIG. 26, both the preamble for transmission synchronization of the reservation signal described with reference to FIG. 24 and the preamble for PDSCH transmission synchronization described with reference to FIG. 25 are transmitted. Subframe synchronization of the licensed band) can be accurately identified. Here, the preamble (Preamble 1) transmitted before the transmission of the reservation signal and the preamble (Preamble 2) transmitted after the transmission of the reservation signal are the same preamble is used so that the receiving side determines which preamble for synchronization acquisition according to the transmission order The two preambles Preamble 1 and 2 may be formed in different sequences. If the two preambles (Preamble 1, 2) are made of different sequences, for example, only the preamble transmitted before the PDSCH transmission may use a sequence generated from the UE identifier.

The preamble described above may be using a time resource corresponding to at least one or more OFDM symbols on the time axis, or the transmission time unit may be determined in consideration of other devices that want to use an unlicensed band.

Meanwhile, although the transmission of the preamble may be performed every PDSCH transmission, in some cases, the preamble may not be transmitted. For example, after transmitting a reservation signal, a preamble, a PDSCH, and the like to one specific terminal, if the PDSCH is transmitted to the specific terminal again within a predetermined time, the transmission of the preamble may be omitted. Alternatively, the transmission of the preamble may be set to be transmitted according to a preset period.

Although the above descriptions have been basically based on the OFDM scheme, embodiments of the present invention may be applied to the OFDMA scheme. That is, as shown in FIG. 23, the unlicensed band may be separated on frequency resources to be configured to perform PUSCH transmission for the terminal 1 and the terminal 2. Other details such as carrier sensing time, unit, PUSCH subframe length, transmission of reservation signal, etc. will be replaced with the above description. In addition, although FIG. 23 illustrates the PUSCH transmission, it can be found that the present invention can be applied to the PDSCH transmission.

Hereinafter, details that may be additionally applied in relation to PDSCH and PUSCH transmission on the unlicensed band described above will be described.

i) DCI transmitted on PDCCH

In the above-described methods, the DCI transmitted on the PDCCH may use existing LTE-A DCI formats as it is. However, the subframe may additionally include information such as a start position, an end position, a length, an MCS, a carrier sensing position, and the like. In particular, in a structure in which one UE occupies the entire unlicensed band for a predetermined time, such as the OFDM scheme, broadcast the start point, end point, length, etc. of a currently occupied packet or transport block. By doing so, it may help for carrier sensing and PDSCH and / or PUSCH transmission.

ii) partial and non-carrier aggregation

When carrier aggregation is partially applied (Partial cross carrier scheduling) or when a PDCCH is transmitted on an unlicensed band, the PDCCH may transmit only some information on PDSCH and / or PUSCH scheduled on the unlicensed band. For example, only MCS information may be included. That is, HARQ, Power Control, and RA information may be excluded. That is, in order to distinguish between which UE the PDSCH is transmitted from and which UE the PUSCH is transmitted from, a specific preamble is transmitted before PDSCH to inform the transmission start position while distinguishing the UE, and the specific preamble is transmitted in front of the PUSCH transmission. It can be informed which UE has transmitted and the PUSCH transmission start position. Here, the preamble may perform a reference signal function as well as terminal classification. In this case, it is possible to find out which terminal the corresponding packet belongs to by using a reference signal generated using a UE ID. Similarly with the PDSCH, the receiving terminal can be known by looking at the reference signal. The location at which this preamble or reference signal is transmitted may be first or last.

iii) transmission power control

The transmit power of the PDSCH and / or PUSCH transmitted on the unlicensed band may use a specified value and may not perform separate power control. That is, the transmission may be set for a designated time at a specified power in an unlicensed band, and the change may be configured through a separate signal. In the OFDMA scheme, most of the proposed rules and methods can be applied.

iv) carrier sensing (CS)

The transmission of the PDSCH or the PUSCH described above was a case where the base station or the terminal of the LTE / LTE-A system uses the entire bandwidth of the unlicensed band. Specifically, for example, in the OFDM scheme of PDSCH transmission, the base station performs carrier sensing for the unlicensed band and if the unlicensed band is available (if necessary, by reserving the unlicensed band through transmission of a reservation signal). In this case, carrier sensing is performed in a unit of time (for example, OFDM symbol) on the time axis for the entire bandwidth of the unlicensed band, and PDSCH transmission has been described for the entire bandwidth of the unlicensed band. . However, even when it is determined that the total bandwidth of the unlicensed band is not available, some bandwidth may not be available because the total bandwidth of the unlicensed bandwidth is wide enough or the bandwidth of the device using the unlicensed band is small. There may be. In this case, you can lower the MCS setting or take the retransmission and perform the transmission, but this is not a fundamental solution. Accordingly, in addition to performing carrier sensing on the time axis described above, a carrier sensing on the frequency axis, a carrier sensing unit, and a resource reservation method for the same are provided.

The carrier sensing unit may be determined by analyzing carrier sensing granularity, transmission bandwidth, accessible bandwidth, search bandwidth, and the like of systems existing in the unlicensed band. Based on this, the unlicensed band can be implicitly or explicitly partitioned, and carrier sensing and resource reservation can be performed. Here, the carrier sensing unit may have several sizes. That is, there is a case where the carrier sensing unit is not configured in one basic unit. Since the carrier sensing unit is determined based on the systems that may exist in the unlicensed band, the number of carrier sensing units will be determined considering the number of systems.

For example, the LTE-A base station or terminal in the unlicensed band system may attempt to perform transmission for the entire 20MHz band, and WiFi may perform carrier sensing and transmission in 5MHz or 10MHz units. In order to perform carrier sensing and reserve resources, the LTE-A system needs to consider 5MHz bandwidth partitioning used by WiFi. If 20MHz is correctly divided into 4 5MHz (ie, band1, band2, band3, and band4), the LTE-A system performs carrier sensing in 5MHz size band unit, checks whether the WiFi system exists, and uses resources if available. Can be reserved. If a specific band band1 is not available, another available band may be selected to perform reservation and transmission.

FIG. 27 illustrates an example in which an LTE-A system and a non-LTE-A system A and B perform carrier sensing in units of a carrier sensing unit suitable for each system and transmit according to the result. For convenience, the carrier sensing unit is divided into the same size, but the actual band partitioning may not be the same. System A performs carrier sensing on a carrier sensing unit basis and transmits (when only a frequency resource corresponding to one carrier sensing unit is required for transmission or one carrier sensing unit is a maximum transmission band). System B is an example of performing carrier sensing in two carrier sensing units and transmitting (when a frequency resource corresponding to two carrier sensing units is required for transmission or two carrier sensing units are the maximum transmission bands). . The LTE-A system may perform carrier sensing on an arbitrary carrier sensing unit according to the size of a packet to be sent and select a usable band therefrom to perform transmission. The same Busy Sensing Interval can be applied in the time domain.

The technique may be performed at the base station or at the terminal. While the base station performs carrier sensing when transmitting from the base station to the terminal (eNB-to-UE), it is common that the terminal performs such carrier sensing when transmitting from the terminal to the base station (UE-to-eNB).

Alternatively, the present invention may operate in a manner that complements carrier sensing. That is, as shown in FIG. 28 (a), when the base station performs carrier sensing, the terminal may not know how to interfere with the base station, and thus, the terminal performs carrier sensing in advance and may reserve the corresponding resource if necessary. If the base station is notified of this, the base station may attempt to transmit by combining the result of the carrier sensing and the carrier sensing information received from the terminal. The terminal may be induced to perform transmission to the recommended (or reserved) resource region. Similarly, referring to FIG. 28 (b), since the UE cannot exactly know the resource collision situation experienced by the base station, the base station can determine the resource situation that the base station is experiencing through carrier sensing (reserving the resource if necessary). Also, it can be informed to the terminal to induce the terminal to perform the transmission to the correct resource region. In this case, such additional information may be obtained through a separate channel for transmitting and receiving information or through an existing physical channel.

v) other

The ACK / NACK for the PDSCH transmission or the ACK / NACK for the PUSCH transmission may be configured to be received immediately after the corresponding packet transmission. In addition, the transmission of the ACK / NACK may be set to be performed only on the licensed band.

The above descriptions can be applied to TDD as well as FDD. In the case of TDD, since the frequency bands of the downlink and the uplink are the same, a license band (LTE-A PCC band) may be represented as one in the drawings.

On the other hand, the operation may be performed more efficiently by, for example, giving an offset so as not to intentionally coincide the subframe boundary in the licensed band and the unlicensed band.

The embodiments described above may be applied alone, but may be applied in a combination of two or more embodiments. For example, when performing both PDSCH and PUSCH transmission in the unlicensed band, it can be understood that Embodiment 2 and Embodiment 3 are simultaneously applied.

29 is a diagram illustrating the configuration of a base station apparatus and a terminal apparatus according to the present invention.

Referring to FIG. 29, the base station apparatus 2910 according to the present invention may include a receiving module 2911, a transmitting module 2912, a processor 2913, a memory 2914, and a plurality of antennas 2915. The plurality of antennas 2915 means a base station apparatus supporting MIMO transmission and reception. The receiving module 2911 may receive various signals, data, and information on the uplink from the terminal. The transmission module 2912 may transmit various signals, data, and information on a downlink to the terminal. The processor 2913 may control the overall operation of the base station apparatus 2910.

The processor 2913 of the base station apparatus 2910 according to an embodiment of the present invention transmits at least one or more of a preamble or a reservation signal when it is determined that the unlicensed band is available through carrier sensing. The PDSCH may be transmitted on an unlicensed band immediately after transmission of at least one of the reservation signals, and the preamble may be for the terminal device to acquire synchronization for reception of the reservation signal or the PDSCH.

In addition, the processor 2913 of the base station apparatus 2910 performs a function of processing information received by the base station apparatus 2910 and information to be transmitted to the outside, and the memory 2914 stores the processed information and the like for a predetermined time. And may be replaced by a component such as a buffer (not shown).

29, the terminal device 2920 according to the present invention may include a receiving module 2921, a transmitting module 2922, a processor 2913, a memory 2924, and a plurality of antennas 2925. have. The plurality of antennas 2925 may mean a terminal device that supports MIMO transmission and reception. The receiving module 2921 may receive various signals, data, and information on a downlink from the base station. The transmission module 2922 may transmit various signals, data, and information on the uplink to the base station. The processor 2913 may control operations of the entire terminal device 2920.

The processor 2913 of the terminal device 2920 according to an embodiment of the present invention receives at least one or more of a preamble or a reservation signal from a base station on the unlicensed band and receives a PDSCH on the unlicensed band. Receiving synchronization of the reservation signal or the PDSCH may be obtained through a preamble.

In addition, the processor 2913 of the terminal device 2920 performs a function of processing information received by the terminal device 2920, information to be transmitted to the outside, and the memory 2924 stores arithmetic information and the like for a predetermined time. And may be replaced by a component such as a buffer (not shown).

Specific configurations of the base station apparatus and the terminal apparatus as described above may be implemented so that the above-described matters described in various embodiments of the present invention may be independently applied or two or more embodiments may be applied at the same time. Omit.

In addition, in the description of FIG. 29, the description of the base station apparatus 2910 may be equally applicable to a downlink transmitting entity or an uplink receiving entity, and the description of the terminal apparatus 2920 is a downlink receiving entity. Alternatively, the same may be applied to a relay device as an uplink transmission entity.

Embodiments of the present invention described above may be implemented through various means. For example, embodiments of the present invention may be implemented by hardware, firmware, software, or a combination thereof.

For implementation in hardware, a method according to embodiments of the present invention may include one or more Application Specific Integrated Circuits (ASICs), Digital Signal Processors (DSPs), Digital Signal Processing Devices (DSPDs), and Programmable Logic Devices (PLDs). It may be implemented by field programmable gate arrays (FPGAs), processors, controllers, microcontrollers, microprocessors, and the like.

In the case of an implementation by firmware or software, the method according to the embodiments of the present invention may be implemented in the form of a module, a procedure, or a function that performs the functions or operations described above. The software code may be stored in a memory unit and driven by a processor. The memory unit may be located inside or outside the processor, and may exchange data with the processor by various known means.

The detailed description of the preferred embodiments of the invention disclosed as described above is provided to enable those skilled in the art to implement and practice the invention. Although the above has been described with reference to preferred embodiments of the present invention, those skilled in the art will understand that various modifications and changes can be made without departing from the scope of the present invention. For example, those skilled in the art can use each of the configurations described in the above-described embodiments in combination with each other. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

The invention can be embodied in other specific forms without departing from the spirit and essential features of the invention. Accordingly, the above detailed description should not be interpreted as limiting in all aspects and should be considered as illustrative. The scope of the invention should be determined by reasonable interpretation of the appended claims, and all changes within the equivalent scope of the invention are included in the scope of the invention. The present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein. In addition, the claims may be combined to form an embodiment by combining claims that do not have an explicit citation relationship or may be incorporated as new claims by post-application correction.

In the above description, the present invention has been described based on a form applied to the 3GPP LTE series mobile communication system, but the present invention may be used in the same or equivalent principles in various mobile communication systems.

Claims (14)

1. In a method for transmitting a signal on an unlicensed band by a base station in a wireless communication system,

   Transmitting at least one of a preamble or a reservation signal when it is determined that the unlicensed band is available through carrier sensing;

   Transmitting a PDSCH on an unlicensed band immediately after transmission of at least one of the preamble or a reservation signal,

   The preamble is a signal transmission method for the terminal to obtain the reception synchronization of at least one of the reservation signal or the PDSCH.
2. The method of claim 1,

   If the preamble is transmitted prior to the reservation signal, the preamble includes information indicating that the transmission of the reservation signal is started.
3. The method of claim 1,

   When the preamble is transmitted after the reservation signal, the preamble is transmitted on a subframe boundary of a licensed band used by the base station.
4. The method of claim 1,

   And if the time when it is determined that the unlicensed band is available is one of a subframe boundary or a slot boundary of the licensed band used by the base station, the reservation signal is not transmitted.
5. The method of claim 1,

   Scheduling information of the PDSCH transmitted on the unlicensed band is transmitted through a PDCCH transmitted on a licensed band used by the base station.
6. The method of claim 1,

   The preamble further comprises identifier information of a terminal receiving the PDSCH.
7. In a method for receiving a signal on an unlicensed band in a wireless communication system,

   Receiving at least one or more of a preamble or a reservation signal from a base station on the unlicensed band;

   Receiving a PDSCH on the unlicensed band,

   The terminal acquires at least one reception synchronization of the reservation signal or the PDSCH through the preamble.
8. The method of claim 7, wherein

   If the preamble is received before the reservation signal, the preamble includes information indicating that transmission of the reservation signal is started.
9. The method of claim 7, wherein

   When the preamble is received after the reservation signal, the preamble is transmitted on a subframe boundary of a licensed band used by the base station.
10. The method of claim 7, wherein

    The preamble or reservation signal is transmitted when the base station determines that the unlicensed band is available through carrier sensing, and the time point when the unlicensed band is determined to be available is used for the subframe boundary of the licensed band used by the base station. Or the reservation signal is not transmitted when it is one of slot boundaries.
11. The method of claim 7, wherein

    Scheduling information of the PDSCH received on the unlicensed band is received via the PDCCH on the licensed band used by the base station.
12. The method of claim 7, wherein

    The preamble further comprises the identifier information of the terminal that receives the PDSCH, the signal receiving method.
13. A base station apparatus in a wireless communication system,

    Transmission module; And

    Includes a processor,

    When the processor determines that the unlicensed band is available through carrier sensing, the processor transmits at least one or more of a preamble or a reservation signal, and transmits a PDSCH on the unlicensed band immediately after transmission of at least one of the preamble or a reservation signal. And the preamble is for a terminal device to obtain reception synchronization of at least one of the reservation signal and the PDSCH.
14. A terminal device in a wireless communication system,

    A receiving module; And

    Includes a processor,

    The processor receives at least one or more of a preamble or a reservation signal from the base station on the unlicensed band and receives a PDSCH on the unlicensed band, and performs reception synchronization of at least one of the reservation signal or the PDSCH through the preamble. Obtaining, the terminal device.

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